Those of you who may have heard one of my "rants" previously, will know that I very much doubt the name Lundy to refer to "Puffin Island" Whilst I don't doubt the Viking root of the name, I believe it refers to something other than the popular and (I accept) generally held definition.
The -ey suffix in Norse does mean "Island" - therefore, as an aside, it is incorrect to refer to Lundy Island: the correct name is simply Lundy. But the controversial element is Lund. The traditional, populist definition is held to refer to the bird, the Puffin. But my understanding is that Lund, in Old Norse, refers to seabirds generally, rather than just the colourful bird we associate the Island with now. But even then, why would the Vikings , having travelled so many hundreds and thousands of miles through the territories of the Puffin, wait until they had arrived at Lundy to name that island after this otherwise ubiquitous bird?
The word Lund, as a place name on dry land, traditionally refers to a copse, or wooded area. On the face of it, the Vikings would only ever refer to the Island as a wooded area if they took a sense of irony to surreal levels, as anyone who knows Lundy would agree. However, I contend that the Island would have looked different to them, given their activities.
Lundy, following a number of weeks of raiding parties either side ot the Bristol,Channel, would have been the first safe haven on the homeward journey. Undefended, some hunting possible for food, and shelter available, it would present a very necessary opportunity to stop and recoup some energy, and make repairs to their ships before the long journey home. It would also be a place to bury their dead: note the Kistvaen in the South West of the Island. If you think about this, it suggests that the Vikings would therefore be approaching from the east:as they approach the open sea, and as anyone who has come in on the Oldenburg will tell you, the Island looks wooded on that aspect, let alone at that time, when it would have been even denser. The importance to the Vikings would be that there was wood readily available, and that would be a reason to refer to the island at all, and certainly as a "wooded area"
The Mystic Realms site, Lundy, Isle of Avalon, mentions another possibility: one that appeals to my own view of the Lundy past, but I would probably have to agree is somewhat less likely.